The wording for Shield of Faith: Force Weapons losetheir ability to kill their target out right, simply count them as power weapons.

In the newest FAQ for them they do not even talk about it.

Instant Death: If a model suffers an unsaved wound from an attack that has a Strength value of double its Toughness value or greater it is killed out right and removed as a casualty. The wording for are force weapon and the 5th ed force weapon are different. so on could argue the point because of the wording and the effects each does.

Why use science and education when ignorance and superstition will work just as well.